could you check what is connected to the two slow databus lines? If they are slower than the others it would seem as if a too large load is connected to them. Might be you could insert a buffer of some kind...
Uwe. Declan Moriarty wrote: > > Was it Ingraham, Andrew who wrote on Friday 06 September 2002 19:36: > > Declan, > > > > This all sounds familiar. Didn't you have a very similar problem a few > > years ago too? Something involving NMOS CPUs and pull-ups? > > I was rooting at this a few years ago. Some of the issue was fixed by pulling > up one particular port on the cpu. That left me with some boartds with > HD6340s which worked, some boards with 6840s which didn't, and couldn't be > made to stand. I had stock, so it wasn't a great issue. but it never got > properly sorted > > > > I haven't touched NMOS in ages (if ever) so I'm certainly no expert ... but > > one might think that they all might have been designed with the same (TTL) > > thresholds. I suppose that would be wishful thinking. > > AFAIK, the cmos thresholds are higher. The bus is clean enough, except for 2 > databus lines which have slow rises. Pulling these high kills the board, > however. The Digital Signature Analyser has a funny impedance (Loads towards > 1.4V) which distorts things, and generally it's a pain. Everything looks OK, > or better. Faults don't show. But the X@$�"! boards don't work! > > -- > Regards, > > Declan Moriarty > > Applied Researches - Ireland's Foremost Electronic Hardware Genius > > A Slightly Serious(TM) Company > > Experience is like a comb, > that Life gives you - AFTER all your hair has fallen out! > -- > Author: Declan Moriarty > INET: [EMAIL PROTECTED] > > Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 > San Diego, California -- Public Internet access / Mailing Lists -- Author: Uwe Zimmermann INET: [EMAIL PROTECTED] Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
